sodium stannate
{{Chembox
| ImageFile = Na2Sn(OH)6.png
| ImageSize =
| ImageAlt = White powder of sodium stannate
| ImageCaption =
| ImageFile1 =
| ImageName1 = Molecular Structure of Sodium Stannate
| IUPACName = Sodium hexahydroxostannate(IV)
| OtherNames = disodium hexahydroxyltin
Sodium stannate(IV)
sodium stannate–3–water
sodium tin(IV) oxide hydrate
|Section1={{Chembox Identifiers
| CASNo = 12027-70-2
| CASNo_Ref =
| PubChem =131868867
| RTECS =
| EINECS = 234-724-5
| ChemSpiderID =145444
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| UNII = NJ7C1V83KG
| StdInChI=1S/2Na.6H2O.Sn/h;;6*1H2;/q2*+1;;;;;;;+4/p-6
| StdInChIKey = PMPBLIIMRRPPEO-UHFFFAOYSA-H
| SMILES = [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Na+].[Na+].[Sn+4]
}}
|Section2={{Chembox Properties
| Formula = H6Na2O6Sn
| MolarMass = 266.73 g/mol
| Appearance = Colorless or white solid
| Density = 4.68 g/cm3
| MeltingPt =
| BoilingPt = N/A
| Solubility =
}}
|Section3={{Chembox Hazards
| ExploLimits =
| ExternalSDS = [http://www.sciencelab.com/msds.php?msdsId=9925038]{{cite web|title=Material Safety Data Sheet – sodium stannate trihydrate MSDS|url=http://www.sciencelab.com/msds.php?msdsId=9925038|publisher=Science Lab|date=21 May 2013|access-date=1 June 2017|archive-date=1 June 2012|archive-url=https://web.archive.org/web/20120601002702/http://www.sciencelab.com/msds.php?msdsId=9925038|url-status=dead}}
| FlashPtC = 57
| AutoignitionPt = N/A
| LD50 = 2132 mg/kg [Mouse]
| MainHazards =
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0
| NFPA-S =
| PEL =
| GHSPictograms = {{GHS05}}{{GHS07}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314|315|319|335|412}}
| PPhrases = {{P-phrases|260|261|264|271|273|280|301+330+331|302+352|303+361+353|304+340|305+351+338|310|312|321|332+313|337+313|362|363|403+233|405|501}}
}}
}}
Sodium stannate, formally sodium hexahydroxostannate(IV), is the inorganic compound with the formula Na2[Sn(OH)6]. This colourless salt forms upon dissolving metallic tin or tin(IV) oxide in sodium hydroxide and is used as a stabiliser for hydrogen peroxide.{{cite book|last = Clark|first = John D.|author-link = John Drury Clark|year = 1972|title = Ignition! An Informal History of Liquid Rocket Propellants|publisher = Rutgers University Press|isbn = 0813507251}} In older literature, stannates are sometimes represented as having the simple oxyanion SnO32−,Similarly, stannites are sometimes represented with the anion SnO22− in which case this compound is sometimes named as sodium stannate–3–water and represented as Na2SnO3·3H2O, a hydrate with three waters of crystallisation. The anhydrous form of sodium stannate, Na2SnO3, is recognised as a distinct compound with its own CAS Registry Number,{{cite web|url = https://pubchem.ncbi.nlm.nih.gov/compound/Sodium_stannate#section=Molecular-Formula|title = Sodium Stannate|publisher = PubChem|access-date = 1 June 2017|author = National Center for Biotechnology Information|author-link = National Center for Biotechnology Information|year = 2017}} {{nowrap|{{CAS|12058-66-1}},}} and a distinct material safety data sheet.{{cite web|url = http://datasheets.scbt.com/sc-229318.pdf|title = Sodium Stannate MSDS|access-date = 1 June 2017|date = 14 June 2011|publisher = Santa Cruz Biotechnology}}
Alkali metal stannate compounds are prepared by dissolving elemental tin in a suitable metal hydroxide, in the case of sodium stannate by the reaction:{{cite book|first1 = Norman N.|last1 = Greenwood|authorlink1 = Norman Greenwood|last2 = Earnshaw|first2 = Alan|year = 1997|title = Chemistry of the Elements|edition = 2nd|publisher = Butterworth-Heinemann|isbn = 0750633654}}
:Sn + 2 NaOH + 4 H2O → Na2[Sn(OH)6] + 2 H2
A similar reaction occurs when tin dioxide is dissolved in base:
:SnO2 + 2 NaOH + 2 H2O → Na2[Sn(OH)6]
The anhydrous form can also be prepared from tin dioxide by roasting with sodium carbonate in a mixed carbon monoxide / carbon dioxide environment:{{cite journal|journal = Hydrometallurgy|volume = 146|year = 2014|pages = 82–88|title = Sodium stannate preparation from stannic oxide by a novel soda roasting–leaching process|first1 = Yuanbo|last1 = Zhang|first2 = Zijian|last2 = Su|first3 = Bingbing|last3 = Liu|first4 = Zhixiong|last4 = You|first5 = Guang|last5 = Yang|first6 = Guanghui|last6 = Li|first7 = Tao|last7 = Jiang|doi = 10.1016/j.hydromet.2014.03.008| bibcode=2014HydMe.146...82Z }}
:SnO2 + Na2CO3 → Na2SnO3 + CO2
The anion is a coordination complex that is octahedral in shape, similar to most stannates, such as the hexachlorostannate anion {{nowrap|[SnCl6]2−}}. The Sn—O bond distances average 2.071 Å.{{cite journal|first1 = Herbert|last1 = Jacobs|first2 = Rainer|last2 = Stahl|title = Neubestimmung der Kristallstrukturen der Hexahydroxometallate Na2Sn(OH)6, K2Sn(OH)6 und {{nowrap|K2Pb(OH)6}}|language = German|journal = Z. Anorg. Allg. Chem.|year = 2000|volume = 626|issue = 9|pages = 1863–1866|doi = 10.1002/1521-3749(200009)626:9<1863::AID-ZAAC1863>3.0.CO;2-M}}